(join-a-simple-domain-with-the-rid-backend)=
# Join a simple domain with the rid backend

Let's expand on the configuration we had for the *rid* backend and complete the `/etc/samba/smb.conf` configuration file with the remaining details. We are joining a single domain called `EXAMPLE.INTERNAL`. The new configuration options were added at the end of the `[global]` section:

    [global]
        security = ads
        realm = EXAMPLE.INTERNAL
        workgroup = EXAMPLE
    
        idmap config * : backend       = tdb
        idmap config * : range         = 100000 - 199999
        idmap config EXAMPLE : backend = rid
        idmap config EXAMPLE : range   = 1000000 - 1999999

        # allow logins when the DC is unreachable
        winbind offline logon = yes
        # this *can* be yes if there is absolute certainty that there is only a
        # single domain involved
        winbind use default domain = no
        # setting these enumeration options to yes has a high performance impact
        # and can cause instabilities
        winbind enum groups = no
        winbind enum users = no
        winbind refresh tickets = yes
        # if domain users should be allowed to login, they will need a login shell
        template shell = /bin/bash
        # the home directory template for domain users
        template homedir = /home/%D/%U
        kerberos method = secrets and keytab

Right after saving `/etc/samba/smb.conf`, it's always good practice to run the `testparm` utility. It will perform a quick syntax check on the configuration file and alert you of any issues. Here is the output we get with the above configuration settings:

    Load smb config files from /etc/samba/smb.conf
    Loaded services file OK.
    Weak crypto is allowed by GnuTLS (e.g. NTLM as a compatibility fallback)

    Server role: ROLE_DOMAIN_MEMBER

    Press enter to see a dump of your service definitions
    (...)


During the domain join process, the tooling will attempt to update the {term}`DNS` server with the {term}`hostname` of this system. Since its IP is likely not yet registered in DNS, that's kind of a chicken and egg problem. It helps to, beforehand, set the hostname manually to the {term}`FQDN`. For this example, we will use a host named `n1` in the `example.internal` domain:

    sudo hostnamectl hostname n1.example.internal

So that the output of `hostname -f` (and also just `hostname`) is `n1.example.internal`.

With the config file in place and checked, and all the other changes we made in the previous section, the domain join can be performed:

    $ sudo net ads join -U Administrator
    Password for [EXAMPLE\Administrator]:
    Using short domain name -- EXAMPLE
    Joined 'N1' to dns domain 'example.internal'

You can now revert the `hostnamectl` change from before, and set the hostname back to the short version, i.e., `n1` in this example:

    sudo hostnamectl hostname n1

As the last step of the process, the `winbind` service must be restarted:

    sudo systemctl restart winbind.service

## Verifying the join

The quickest way to test the integrity of the domain join is via the `wbinfo` command:

    $ sudo wbinfo -t
    checking the trust secret for domain EXAMPLE via RPC calls succeeded

The next verification step should be to actually try to resolve an existing username from the domain. In the `EXAMPLE.INTERNAL` domain, for example, we have some test users we can check:

    $ id jammy@example.internal
    uid=1001103(EXAMPLE\jammy) gid=1000513(EXAMPLE\domain users) groups=1000513(EXAMPLE\domain users),1001103(EXAMPLE\jammy)

Another valid syntax for domain users is prefixing the name with the domain, like this:

    $ id EXAMPLE\\jammy
    uid=1001103(EXAMPLE\jammy) gid=1000513(EXAMPLE\domain users) groups=1000513(EXAMPLE\domain users),1001103(EXAMPLE\jammy)

And finally, attempt a console login:

    n1 login: jammy@example.internal
    Password:
    Welcome to Ubuntu 24.04 LTS (GNU/Linux 6.5.0-26-generic x86_64)
    (...)
    Creating directory '/home/EXAMPLE/jammy'.
    EXAMPLE\jammy@n1:~$

The output above also shows the automatic on-demand home directory creation, according to the template defined in `/etc/samba/smb.conf`.

```{note}
The actual login name used can have multiple formats: `DOMAIN\user` at the terminal login prompt, `DOMAIN\\user` when referred to in shell scripts (note the escaping of the '`\`' character), and `user@domain` is also accepted.
```